Search

Quarkonia production in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV had been studied at LHCb using the 2015 and 2018 datasets, separately. While only J/ψ production studies could be done in 2015, thanks to the increased statistics of the 2018 data sample, ψ(2S) has been accessed as well. [ABSTRACT FROM AUTHOR]

We investigate the charmonium and bottomonium production in pp collisions using the Wigner densities formalism. The Wigner density of the quarkonia is approximated by analytical 3-D isotropic harmonic oscillator Wigner densities with the same root-mean-square radius given by the solution of the Schrödinger equation. This approach reproduces quite well the available experimental transverse momentum and rapidity distributions. [ABSTRACT FROM AUTHOR]

One of the findings of the LHC heavy ion program is the observation of stronger suppression of the excited quarkonium states compared to the ground states in lead-lead (PbPb) and proton-lead (pPb) collisions. Such differences among the states may imply dissociation effects occurring at late stages, after the evolution of heavy quark pairs into well-defined physical states. The variety of binding energies within the quarkonia families offers an experimental tool to characterize the phenomena at play. Measuring the excited states is crucial as they represent significant feed-down contributions to the production of the ground states and must be accounted for in the interpretation of the data. We present studies of the relative suppression of quarkonia in pPb and PbPb collisions performed by CMS. For the first time, the nuclear modification factor has been extended to the strongly suppressed Υ(3S) state. Moreover, nuclear modification factors as well as excited-to-ground state cross section ratios are measured as a function of particle transverse momentum and rapidity, and event activity. The results are compared with several model calculations incorporating initial- and final-state effects. [ABSTRACT FROM AUTHOR]

The PHENIX experiment at RHIC has a unique large rapidity coverage (1.2 < |y| < 2.2) for heavy flavor studies in heavy-ion collisions. This kinematic region has a smaller particle density and may undergo different nuclear effects before and after the hard process when compared to mid-rapidity production. The latest PHENIX runs contain a large data set which allows, for the first time, the study of heavy flavor and J/ψ flow at the large rapidity region in Au+Au collisions at √SNN =200 GeV. This measurement has the potential to reveal a medium evolution distinct from that known at mid-rapidity. [ABSTRACT FROM AUTHOR]

The multiple parton−parton interactions (MPIs) are an important element to describe the observed collective flow and strangeness enhancement in high multiplicity pp and p−Pb collisions, the so-called small systems. At LHC energy, MPIs affect both soft and hard scales of the event. Since quarkonium production involves both, it can be an excellent tool to understand the role of MPIs in small systems. Study of multiplicity dependent quarkonium production provides an indirect probe of MPIs in hadronic collisions. Also, relative production of excited-to-ground quarkonium states as a function of multiplicity are sensitive to final state effects. Cross section measurements of different quarkonium states are also important to understand their production mechanisms. In these proceedings, first preliminary results of ψ(2S)-over-J/ψ cross section measurements at mid and forward rapidity (y) from Run 2 and Run 3 pp collisions at √S and 13.6 TeV, respectively will be presented. Preliminary results on ϒ(nS) states (n = 1,2) cross sections and final multiplicity dependent measurements of excited-to-ground states quarkonium yields, at forward y, in pp collisions at √S TeV will be shown. In addition, few performance plots from Run 3 in the quarkonium sector will be presented and discussed. [ABSTRACT FROM AUTHOR]

We report the measurements of quarkonia (J/ψ and ψ(2S)) in heavyion collisions via the e+e− decay channel at midrapidity (|y| < 1) by the STAR experiment. The centrality and transverse momentum dependence of the yield ratio of ψ(2S) to J/ψ is measured for the first time in heavy-ion collisions at RHIC. These results, together with the new measurement of collision energy dependence of inclusive J/ψ suppression in Au+Au collisions, allow for a systematic study of the quarkonium production in the medium. In addition, we present the first measurement of J/ψ polarization in heavy-ion collisions at RHIC in both the Helicity and the Collins-Soper frames, which provides a new insight for studying the properties of the Quark-Gluon Plasma created in heavy-ion collisions. [ABSTRACT FROM AUTHOR]

We report on progress in the nonperturbative understanding of quarkonium dynamics inside a thermal plasma. The time evolution of small-size quarkonium is governed by two-point correlation functions of chromoelectric fields dressed with an adjoint Wilson line, known in this context as generalized gluon distributions (GGDs). The GGDs have been calculated in both weakly and strongly coupled plasmas by using perturbative and holographic methods. Strikingly, the results of our calculations for a strongly coupled plasma indicate that the quarkonium dissociation and recombination rates vanish in the transport descriptions that assume quarkonium undergoes Markovian dynamics. However, this does not imply that the dynamics is trivial. As a starting point to explore the phenomenological consequences of the result at strong coupling, we show a calculation of the ϒ(1S) formation probability in time-dependent perturbation theory. This is a first step towards the development of a transport formalism that includes non-Markovian effects, which, depending on how close the as of yet undetermined nonperturbative QCD result of the GGDs is to the strongly coupled N = 4 SYM result, could very well dominate over the Markovian ones in quark-gluon plasma produced at RHIC and the LHC. [ABSTRACT FROM AUTHOR]

This is a theoretical overview of the new results regarding open heavy flavor and quarkonium presented in the Quark Matter 2023 conference. [ABSTRACT FROM AUTHOR]

Quarkonium provides a golden probe of the formation of the Quark Gluon Plasma (QGP). Its production in heavy-ion collisions can be affected by an interplay of different phenomena such as medium-induced dissociation and heavy-quark (re)combination in the QGP, and cold nuclear matter effects due to the presence of the nucleus. The measurement of quarkonium states in different collision systems and beam energies allows to gain further insights on these effects and probe the properties of the QGP. In these proceedings, an overview of the main experimental quarkonium measurements in proton-proton, protonnucleus and nucleus-nucleus collisions is presented, giving emphasis on the most recent results from the Large Hadron Collider and Relativistic Heavy Ion Collider experiments shown at the 2023 Quark Matter conference. [ABSTRACT FROM AUTHOR]

Quarkonia are excellent probes of deconfinement in heavy-ion collisions. For J/ψ, a bound state of cc¯ c c ¯ quarks, the (re-)generation is found to be the dominant production mechanism at the LHC energies. Production measurements of non-prompt J/ψ, originating from beauty-hadron decays, allow one to access the interaction of beauty-quarks with the quark-gluon plasma (QGP). Polarization and spin alignment measurements can be used to investigate the characteristics of the formed medium. Moreover, it has been hypothesized that quarkonium states can be polarized by the strong magnetic field generated in the initial state of the collision and by the large angular momentum of the medium in non-central heavy-ion collisions. In these proceedings, the measurements of the inclusive, prompt, and non-prompt J/ψ nuclear modification factor RAA in Pb–Pb collisions at √SNN = 5.02 TeV s NN = 5.02  TeV are shown. The measured non-prompt J/ψ fraction extends down to very low pT with a significantly improved precision compared to previous publications. The results from the first publication on the J/ψ polarization with respect to the event-plane in Pb–Pb collisions at √SNN = 5.02 TeV s NN = 5.02  TeV at forward rapidity are presented as well. The results are compared with available calculations. [ABSTRACT FROM AUTHOR]

Abstract. Quarkonium production in hadronic collisions provides a unique testing ground for understanding quantum chromodynamics (QCD) since it involves both perturbative and non-perturbative regimes of this theory. A variety of experimental observables, such as the production cross-section, polarization, particle correlations, serve as insights into the phenomenology of the quarkonium production and help constrain the theoretical models. Measurements of quarkonia as a function of multiplicity probe multiple parton interactions (MPI), i.e., several parton-parton interactions occurring in a single hadron-hadron collision. Finally, measurements of the azimuthal correlation structure of emitted particles in high multiplicity pp collisions can probe the existence of collective behaviour in small systems. The ALICE detector can reconstruct inclusive quarkonia over a broad kinematical range, spanning from mid-rapidity up to forward rapidity, and down to zero transverse momentum. In addition, at midrapidity, the non-prompt charmonium contribution can be separated from the prompt contribution. In these proceedings, we present new results on the inclusive, prompt and non-prompt J/ψ production cross sections measured by ALICE in pp collisions at different collision energies. The self-normalized ψ(2S)-to-J/ψ yield ratio measurement is investigated as a function of the charged particle multiplicity in pp collisions at √S = 13. TeV s = 13  TeV . Finally, the first measurement of the J/ψ elliptic flow (v2) in high multiplicity pp collisions at √S = 13. TeV s = 13  TeV is presented. Results will be compared to theoretical models. [ABSTRACT FROM AUTHOR]

The second-order Fourier coefficients (v2) of Υ(1S) and J/ψ mesons in high-multiplicity pPb collisions are studied using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 8.16 TeV. The dimuons used to reconstruct the quarkonium states are correlated with charged hadrons using the long-range two-particle correlation technique. The measurement of the Υ(1S) v2 is reported for the first time in small collision systems. The results are discussed in terms of collectivity and modification of heavy quarks. [ABSTRACT FROM AUTHOR]

We report the current understanding of heavy quarkonium production at high transverse momentum (pT) in hadronic collisions in terms of QCD factorization. In this presentation, we highlight the role of subleading power corrections to heavy quarkonium production, which are essential to describe the pT spectrum of quarkonium at a relatively lower pT. We also introduce prescription to match QCD factorization to fixed-order NRQCD factorization calculations for quarkonium production at low pT. [ABSTRACT FROM AUTHOR]

We review the current status of heavy quarkonium production phenomenology based on nonrelativistic effective field theories, focusing on spintriplet S -wave states such as J/ψ, ψ(2S), and ϒ. We present some representative examples for heavy quarkonium production mechanisms proposed in the literature, which vary significantly depending on the choice of data employed in analyses. We then discuss the rôle of polarization in discriminating between the different possible scenarios for quarkonium production. Other observables that may be useful in pinpointing the production mechanism are also introduced, such as the ηc production, associated production of J/ψ plus a gauge boson, and J/ψ production at the Electron-Ion Collider. [ABSTRACT FROM AUTHOR]

The discovery of hadronic states beyond the conventional two-quark meson and three-quark baryon picture in the last two decades is one of the most amazing accomplishments in fundamental physics research. Many experiments contributed to this field despite of the original goals of the design. We review the experimental progress on the study of the quarkoniumlike states — states with at least one heavy quark-antiquark pair and possible light quarks, also known as XYZ states. We give a general review and then focus on the new experimental results on the X(3872) and its bottom-quark partner Xb, the X(3960), the Y(4260), Y(4500), Y(4660), and Y(10750), and the charged charmoniumlike Zc and Zcs states. The observations suggest that we did observe hadronic molecules and we also observed hadronic states with some other quark configurations. Possible further studies at the existing and future facilities are briefly discussed. [ABSTRACT FROM AUTHOR]

In this proceedings contribution, I review recent work that aims to provide a more comprehensive and systematic understanding of bottomonium dynamics in the quark-gluon plasma using an open quantum system (OQS) approach that is applied in the framework of the potential non-relativistic QCD (pNRQCD) effective field theory and coupled to realistic hydrodynamical backgrounds that have been tuned to soft hadron observables. I review how the computation of bottomonium suppression can be reduced to solving a Gorini- Kossakowski-Sudarshan-Lindblad (GKSL) equation for the evolution of the bb̅ reduced density matrix, which includes both singlet and octet states plus medium-induced transitions between them at next-to-leading order (NLO) in the binding energy over temperature. Finally, I present comparisons of phenomenological predictions of the NLO OQS+pNRQCD approach and experimental data for bottomonium suppression and elliptic flow in LHC 5.02 TeV Pb-Pb collisions obtained using both smooth and fluctuating hydrodynamic initial conditions. [ABSTRACT FROM AUTHOR]

The baryon structure may be modified in nuclear medium. The quark meson coupling model predicts that the beta decay rate of a Λ hyperon in Λ hypernuclei decreases by 20% at maximum. We propose an experiment to precisely measure the beta-decay rate of 5ΛHe at J-PARC via the (π+, K+) reaction. A feasibility study via GEANT4 simulation has been done, showing that the background can be suppressed down to ~ 3.9% of the betadecay electron yield, using a calorimeter covering the whole solid angle around the target. The measurement of the beta-decay of a Λ in a nucleus is found to be feasible. [ABSTRACT FROM AUTHOR]

In these proceedings, we present the measurements of inclusive J/ψ production at mid-rapidity region (|y| < 1.0) in Au+Au collisions at √SNN = 54.4 GeV by the STAR experiment. The dependences of nuclear modification factor (RAA) on centrality and transverse momentum (pT) are presented and compared to model calculations. No significant energy dependence of RAA is found within uncertainties. We also report the distribution of z(J/<) = pTJ/ 10 GeV/c and pTJ/< > 5 GeV/c in p+p collisions at √S = 500 GeV. Comparisons to model calculations are presented and physics implications are discussed. [ABSTRACT FROM AUTHOR]

Studies of quarkonium production in heavy-ion collisions can be used for probing QGP properties. The suppression and regeneration of bound quarkonium states is sensitive to the medium properties. Modifications of the quarkonium polarization in Pb–Pb collisions with respect to pp collisions may give further insight into the suppression and regeneration mechanisms in the QGP. Quarkonia are also sensitive to the initial stages of heavy-ion collisions, and measurements in photonuclear collisions may help constrain the nuclear gluon-distribution at low Bjorken-x. In this work, recent quarkonium measurements performed by ALICE in Pb–Pb collisions at √SNN = 5.02 TeV $\sqrt {{S_{{\rm{NN}}}}} = 5.02\,{\rm{TeV}}$ S NN = 5.02   TeV will be discussed. Preliminary measurements of the inclusive J/ψ RAA measured at both forward and central rapidity will be presented. The J/ψ polarization measured for the first time in Pb–Pb collisions, as well as preliminary measurements of the coherent J/ψ photoproduction cross section, will be discussed. [ABSTRACT FROM AUTHOR]

In recent years, a significant theoretical effort has been made towards a dynamical description of quarkonia inside the Quark-Gluon Plasma (QGP), using the open quantum systems formalism. In this framework, one can get a real-time description of a quantum system (here the quarkonium) in interaction with a thermal bath (the QGP) by integrating out the bath degrees of freedom and studying the system reduced density matrix. We investigate the real-time dynamics of a correlated heavy quark-antiquark pair inside the QGP using a quantum master equation previously derived from first QCD principles in [4]. The full equation is directly resolved in 1D to lessen computing costs and is used for the first time to gain insight on the dynamics in both a static and evolving medium following a Björken-like temperature evolution. [ABSTRACT FROM AUTHOR]

The strong suppression of bottomonia production in ultra-relativistic heavy-ion collisions is a smoking gun for the creation of a deconfined quarkgluon plasma (QGP). In this proceedings contribution, I review recent work that aims to provide a more comprehensive and systematic understanding of bottomonium dynamics in the QGP through the use of pNRQCD and an open quantum systems approach. This approach allows one to evolve the heavyquarkonium reduced density matrix, taking into account non-unitary effective Hamiltonian evolution of the wave-function and quantum jumps between different angular momentum and color states. In the case of a strong coupled QGP in which Ebind ≪ T, mD ≪ 1=a0, the corresponding evolution equation is Markovian and can therefore be mapped to a Lindblad evolution equation. To solve the resulting Lindblad equation, we make use of a stochastic unraveling called the quantum trajectories algorithm and couple the non-abelian quantum evolution to a realistic 3+1D viscous hydrodynamical background. Using a large number of Monte-Carlo sampled bottomonium trajectories, we make predictions for bottomonium RAA and elliptic flow as a function of centrality and transverse momentum and compare to data collected by the ALICE, ATLAS, and CMS collaborations. [ABSTRACT FROM AUTHOR]

We study exclusive quarkonium production in the dipole picture at next-to-leading order (NLO) accuracy, using the non-relativistic expansion for the quarkonium wavefunction. The quarkonium light cone wave functions needed in the dipole picture have typically been available only at tree level, either in phenomenological models or in the nonrelativistic limit. Here, we discuss the compatibility of the dipole approach and the non-relativistic expansion and compute NLO relativistic corrections to the quarkonium light-cone wave function in light-cone gauge. [ABSTRACT FROM AUTHOR]

We study the transitions between the different color states of a static quark-antiquark pair, singlet and octet, in a thermal medium. This is done non-perturbatively exploiting the infinite mass limit of QCD. This study is interesting because it can be used for future developments within the framework of Effective Field Theories (EFTs) and because it can be combined with other techniques, like lattice QCD or AdS/CFT, to gain non-perturbative information about the evolution of quarkonium in a medium. We also study the obtained expressions in the large Nc limit. This allows us to learn lessons that are useful to simplify phenomenological models of quarkonium in a plasma. [ABSTRACT FROM AUTHOR]

A coupled-channel approach including the ΛcD¯(*) Λ c D ¯ * and ηcp channels in addition to the Σc(*)D¯(*) Σ c (*) D ¯ (*) and J/ψp channels, as required by unitarity and heavy quark spin symmetry (HQSS), is applied to the hidden-charm pentaquark Pc states, i.e., Pc(4312), Pc(4440) and Pc(4457), discovered by LHCb Collaboration. It is demonstrated that to obtain cutoff independent results, the one-pion exchange potential in the multichannel systems is to be supplemented with next-leading order counter terms responsible for the S-wave-to-D-wave transitions. We show that the experimental data for the J/ψp mass distributions are fully in line with the ΣcD¯ Σ c D ¯ and ΣcD¯* Σ c D ¯ * hadronic molecular interpretation of the Pc(4312) and Pc(4440)/Pc(4457), respectively. A narrow Σc*D¯ Σ c * D ¯ molecule around 4.38 GeV is required by the HQSS with the evidence for its existence seen in the J/ψp spectrum. Moreover, we predict the line shapes for the elastic and inelastic channels. [ABSTRACT FROM AUTHOR]

We compute NRQCD long-distance matrix elements that appear in the inclusive production cross sections of P-wave heavy quarkonia in the framework of potential NRQCD. The formalism developed in this work applies to strongly coupled charmonia and bottomonia. This makes possible the determination of color-octet NRQCD long-distance matrix elements without relying on measured cross section data, which has not been possible so far. We obtain results for inclusive production cross sections of χcJ and χbJ at the LHC, which are in good agreement with measurements. [ABSTRACT FROM AUTHOR]

The Born-Oppenheimer approximation provides a description of heavy-quark mesons firmly based on lattice QCD, but its validity is limited to the lightest states lying far below the first open-flavour meson-meson threshold. This limitation can be overcome in the diabatic framework, a formalism first introduced in molecular physics, where the dynamics is encoded in a potential matrix whose elements can be derived from unquenched lattice QCD studies of string breaking. The off-diagonal elements of the potential matrix provide interaction between heavy quark-antiquark and meson-meson pairs, from which the mixing of quarkonium states with molecular components and the OZI-allowed strong decay widths are directly calculated. This allows for a QCD-based unified description of conventional quarkonium and unconventional mesons containing quark-antiquark and meson-meson components, what has proved to be successful for charmoniumlike and bottomoniumlike resonances. [ABSTRACT FROM AUTHOR]

The width difference ΔΓs that can be extracted from lifetime measurements of the two mass eigenstates of the Bs0−B¯s0 B s 0 − B ¯ s 0 system is one of the key flavor precision observables and has been experimentally measured at per cent level accuracy. The current theory prediction is much less accurate and a sizable reduction of scale uncertainties can only be achieved by means of evaluating the uncalculated 2- and 3-loop QCD corrections. This is precisely the issue addressed in this work where we report on the results that have been obtained so far and explain some of the technical and conceptual challenges that we encountered in the course of our calculations. [ABSTRACT FROM AUTHOR]

We review recent progress in open quantum system approach to the description of quarkonium in the quark-gluon plasma. A particular emphasis is put on the Lindblad equations for quarkonium and its numerical simulations. [ABSTRACT FROM AUTHOR]

This is a discussion about open quantum systems and its application to the study of hard probes. It reviews some of the things that were said in the corresponding round table. Views are only my own. [ABSTRACT FROM AUTHOR]

The width difference ΔΓs that can be extracted from lifetime measurements of the two mass eigenstates of the Bs0−B¯s0 B s 0 − B ¯ s 0 system is one of the key flavor precision observables and has been experimentally measured at per cent level accuracy. The current theory prediction is much less accurate and a sizable reduction of scale uncertainties can only be achieved by means of evaluating the uncalculated 2- and 3-loop QCD corrections. This is precisely the issue addressed in this work where we report on the results that have been obtained so far and explain some of the technical and conceptual challenges that we encountered in the course of our calculations. [ABSTRACT FROM AUTHOR]